1.   Brian thought his neck was going to break, and his knees buckled and he slid down to the ground.

2.   Then my knees buckled and I toppled into the warm water, laughing uproariously.

3.   They were small then, but sometimes our knees buckled under their weight.

4.   His words hit her like a battering-ram, making her knees buckle beneath her.

5.   For a helpless moment she thought her knees might buckle.

6.   As the stunned Norris fell to the floor, his right knee buckled under him and he lay flat on his back.

7.   But his knees were buckling even before he hit the Hub.

8.   Clinton laughed so hard that his knees buckled and his face turned the color of cabernet.